A conventional closure is described in U.S. Pat. No. 5,485,871, according to which a tank filling pipe is provided with an airtight shut-off valve. The valve cover can be unlocked by operating a button, so that it can be moved by the filling nozzle to the inside of the tank filling pipe.
This is problematical due to the fact that the closure mechanism can easily be damaged by improper handling or an accident because it projects out of the tank filling pipe. This is a disadvantage on motor vehicles in particular when this mechanism projects out of the body of the vehicle.
Moreover, the device described in U.S. Pat. No. 5,485,871 is technically complicated and therefore expensive and susceptible to malfunction.